Beverage containers, such as beverage cans, are filled with beverages, such as beer, soft drinks, etc., in a can filling machine just prior to the application of the top of the can in a seamer machine. In order to increase productivity and speed of production, can filling machines have been designed to operate at high speeds. Typical high speed can filling machines are capable of filling cans at a rate of about 1,800 cans per minute. In order to meet state and federal requirements, it is necessary that each can passing through the can filling machine be filled with at least the number of fluid ounces stated on the can. In order to accomplish this, it is a general practice to overfill each can and then remove some product by foaming with a bubble breaker and an undercover gasser. This becomes lost product. In one particular operation wherein the cans are for twelve fluid ounces and the product is a particular brand of beer, the weight for a properly filled can is 374 grams. In view of the extremely high number of cans being filled, it is economically advisable to exceed this overfill weight as little as possible. A control resulting in the savings of one gram of the beer per container is very significant. Therefore, it is highly desirable to have an accurate control on the liquid level of the liquid being deposited into a can by each can filler unit on a can filling machine. In one type of can filler units, a vent tube mounted on a stirrup is used to control the liquid level of the fill in a can. In order to adjust the liquid level, it is necessary to remove the stirrup, perform machining operations and remount the stirrup. In another type of a can filler unit, you can use shims to adjust the position of ball cage level controls, but this system is inconvenient and time consuming.